Guest Time
by Nakama.27
Summary: It's not everyday Karasuma meets the World's Greatest Hitman or his young student, and again, it's really not everyday someone lands a good blow on Koro-sensei. Oneshot


**Maybe it's just me, but it irks me when I see people call Tsuna Tsuna unless they're close w him ykno. I always see adults just referring to his name, and his classmates and friends as Tsuna.**

"It's quite a surprise to see you here," Karasuma said politely, knowing the man wasn't one to be reckoned with. Irina stopped annoying him, her attention focused on the third and fourth participants in the room. She grew rather serious, slightly tense.

"You could say we were passing by."

"How much do you know about the target?" he then asked, careful with his words. One slip up and he may as well be killed on the spot, knowing the hitman before him. Karasuma may be a trained assassin, but the man before him was the _world's greatest hitman_. He was far stronger than him. They wouldn't just randomly drop by the school for no reason, either.

"The basic info we could get," said the teenager beside him. He then lowered his gaze as the hitman glared at him for his big mouth. The teenager, was one Karasuma didn't necessarily recognize. He was a youngster, perhaps the same age as the students of 3-E. His features were that of an innocent child, he would've guessed at first sight, but his eyes held knowledge. Looks had always been deceiving, Karasuma knew all too well. Perhaps he was a student of the hitman.

"What are you doing here?" Irina spoke up, keeping unusually calm. "This is a school, not the type of place for you to be here."

She was uncomfortable, he realized. The well-being of the students wasn't something she dawned over much, but the aura of the man was intimidating her. Perhaps she thought—no, she _knew_ this man could kill all the students in an instant. Karasuma knew this fact, too. He was a dangerous individual.

"We aren't here to kill him," the boy spoke up, with a small, reassuring smile. He seemed like he wanted to say more, but wisely kept his mouth shut.

That smile was all Karasuma needed to remember who this boy was. He wasn't a hitman's student. Yes, technically he was, but he wasn't a hitman himself. He was the _Vongola_ mafia boss, trained under a hitman. Karasuma was never one to involve himself in the mafia, it wasn't his world to dwell in. But of course, he knew certain names and certain people, such as the hitman before him. He heard rumors of the young Vongola Tenth before him, but had yet to see him, much less in person, anyway. There was a sudden, newfound respect for the youngster in the room.

"He's teaching now, isn't he?" the hitman asked. Neither he or Irina responded, not out of suspicion or anything, just mere hesitation. Of course, the young Tsunayoshi before him was the hitman's boss, and one major characteristic known to many was his just actions, a rare boss out of many. Hopefully, if these words were true, then they really weren't here to kill Koro-sensei. The hitman smirked, and said, "A little surprise wouldn't hurt."

The teen beside him looked hesitant at the hitman's words, chuckling nervously.

"R-Reborn.. I don't think you should—"

"It's payback," Reborn said simply, "We go a way's back."

The young mafia boss wisely decided not to fight back, falling silent with him and Irina. He didn't order the hitman to stay, nor necessarily allowed him to leave—more like, whatever he'd say would get him in a situation where he would need "more training," which he _really_ didn't want. Reborn left the room, leaving Tsunayoshi, Karasuma, and Irina somewhat stunned.

Once he left, the young boss let out a deep sigh. Irina seemed to relax slightly, but Karasuma wasn't going to let his guard down easily.

"I'm sorry about that," the boy said meekly, smiling sheepishly. "But, we really were passing by and Reborn said he wanted to catch up with an old friend."

"Erm," Irina began hesitantly, "Not to be rude, but who are you?"

Irina was a hitwoman, of course she'd know Reborn. If he couldn't remember Tsunayoshi right away, the chances she'd know him would probably be low. The young mafia boss smiled knowingly.

"My name is Sawada Tsunayoshi," he said, brown eyes glowing with amusement. Irina's eyes widened in realization, her posture straightening ever so slightly. She knew who he was, for sure.

Before any further conversation could take flight, a gunshot fired through the campus, followed by a few shrieks—most likely from the female students. The young mafia boss didn't flinch, rather, his face contorted to a wry smile—he knew something like this would happen. He sighed softly, turning to him and Irina.

"He's not going to hurt your students," he reassured, and something about his smile caused Karasuma to relax. Of course, he had occasional contacts to mafioso and mafia bosses, but as usual, they were ready to kill anyone at their fingertips. This boy, not just from young age ( he had so much wisdom behind those eyes he was beginning to doubt if the boy was even the same age as his students ), but his character seemed pure and just.

Irina had mentioned to him once, the most interesting thing she found about the mafia families were their ability to manifest a kind of flame from their dying wills. Whatever flame they possessed represented their character, the boss usually being a sort of harmonization factor. If that was the case, it would explain the calming aura the teen possessed.

"Irina-san, right? I heard about you from Lovro-san," he then said. "You're... Karasuma-san?"

Both he and Irina nodded curtly.

Another scream, a boy's name— _Karma_ —echoed through the small building, and that meant it was time to see what exactly was going on.

Upon entering the classroom, Karma stood face-to-face with Reborn, a lazy smirk on his face. Immediately, Tsunayoshi was the first to react to this.

"H-Hey, I don't think you know what you're up against!" he cried, " _Reborn_ , don't hurt him!"

"What, pipsqueak, you his boss or something?" Terasaka called out.

 _Oh the irony_ , Karasuma noted dryly. Tsunayoshi didn't say anything to the boy, either ignoring it, or didn't bother about it. The yellow octopus had two tentacles fallen, a part of his face gone. The hitman must've landed quite a blow upon entering the class. Reborn smirked, his gaze shifting toward his young boss.

"I'm not stupid enough to kill one of _his_ students, dame-Tsuna."

" _Nurufufufufu_.. You're as strict as always, Reborn-san, that's what they call you now?" Koro-sensei said, his tentacles regenerating at a rapid rate.

"They call you Koro-sensei now, huh?" Reborn shot back, lowering his gun.

"Karma-kun, please return to your seat," Koro-sensei advised. "We will resume class shortly."

The said redhead's smirk didn't leave his face as he obediently returned to his seat. Reborn walked toward the door, waiting for Tsunayoshi to follow along. Koro-sensei turned his gaze to the young boss.

"Tsunayoshi-kun? I believe this is the first time we've met, it's a pleasure to meet you," he said, holding out a tentacle. The young Vongola Tenth had a charismatic smile as he held his hand out, shaking it, and nodding in return.

"Koro-sensei, who is he?" came Kayano's voice. The yellow octopus laughed knowingly, shifting his gaze to the green-haired girl.

"He's an acquaintance of mine," he said.

"Is he an assassin?" asked Nagisa.

"He's the student of a hitman," said Irina. She casted a glance at Karasuma, and he knew what she meant. It was the most plausible thing to say. It was best for the students to not be familiar with the mafia, and of course, Tsunayoshi knew that too. It didn't imply if he was an assassin or a hitman, simply, he trained under one.

"Who's the guy that attacked Koro-sensei?" asked Sugino.

"My name is Reborn," the hitman said, smirking. "I'm _dame_ -Tsuna's tutor, and I'm giving you all the opportunity to go against my student, if your teacher allows it."

"Oh, of course!" Koro-sensei chirped. "Any volunteers?"

The class was shunned silent. Firstly, the man managed to get a good hit on their target, on the first day of meeting him. Sure, Karma'd done so, but this hitman landed more than just a simple handshake, without even much greeting to the octopus. He seemed strong, _stronger_ than Karasuma or Irina. Secondly, despite the hitman's student seemingly a weak looking kid, if he was taught by that man, then, they didn't want to risk their life. Looks were deceiving, something they knew pretty well throughout the classroom.

"What happens if we beat him?" Itona asked, suddenly curious. This arose the students' curiosity.

"Perhaps you might be able to land a blow on your teacher, if you can beat my student," Reborn said, after a bit of silence. His student was an agile person in combat, although definitely not as fast as Koro-sensei, landing a good hit on him may as well be a step closer to getting a scratch on their teacher. Reborn wanted to silently add, _and see the training my idiotic student will have to go through because assassin trainees defeated him_. But that was a surprise, even for Tsunayoshi. Because, no matter what, the Vongola Tenth will always be his student.

"Are you saying he's fast?" Karma asked, his eyes filled with mischief.

"I'm saying he's strong," Reborn said back. He had pride in his students. Dino may still be a klutz without his subordinates, but he was strong. Tsunayoshi was still learning, always a little needy when it came to important decisions, unlike his first student, who had much confidence in his decisions in the first place. But he really didn't mind the thought of bumping up his second student's training if he lost.

None failed to notice the sudden tense figure of Tsunayoshi.

"When is a good time?" he managed to say, chuckling lightly and nervously.

"P.E.!" the octopus exclaimed cheerfully. Karasuma looked like he was doing to kill him later. The young boss cringed.

"We shouldn't disturb their studies," the assassin said curtly, implying the four of them should leave. With a slide of the door, they were all gone, leaving Koro-sensei and the students with each other.

And the poor octopus, left alone, was bombarded with questions—both classified and ones he really had no idea how to answer, because, he never saw the Vongola Tenth fight before.

Meanwhile, Karasuma shot a look at Reborn.

"With all due respect, how exactly will the students benefit from this? You use different methods compared to assassins," he uttered angrily.

"Confidence boosts skill," said Reborn. "Tsuna's fast but he's not good with hand combat."

"I.." but Tsunayoshi couldn't protest. It was true. He had his gloves, but with _Dying Will Flame_ s, not actual hand to hand combat experience. He may be able to block hits, but he couldn't appear in his _Hyper Dying Will Mode_ without arising questions.

"How do you expect me to do this?!" he then shrieked. "I can't use my flames, and you yourself said I suck at hand combat!"

Karasuma hadn't expected this side of the Vongola Tenth, but it was natural, he assumed. He was still a child, only sixteen. He still needed guidance.

"Figure it out yourself, dame-Tsuna."

The boy had expressive eyes, filled with complaint and denial. Defeated, he sighed and nodded. He must've been through similar conversations before.

Reborn then left the campus, leaving his student in Karasuma's care. Apparently he had important business to attend to ( probably to see if the espresso in the area tasted good, the teen remarked dryly ). Once again, the three of them had been in the teacher's room, silent. Irina had tried to start a conversation, but she often fell silent, deciding not to speak. It was then Tsunayoshi eventually spoke up.

"Karasuma-san, Irina-san, thank you."

Irina smiled gently, something she didn't often do. Karasuma merely nodded in response.

"You're allowed to talk with the students during their lunch period," Karasuma said idly. The Vongola Tenth made no response, but seemed rather grateful at the offer.

During lunch period, right before Koro-sensei left the classroom, Tsunayoshi entered silently, but none failed to capture his entrance.

"Oh, so our opponent decides to sneak info on us," Karma said smoothly.

When the octopus disappeared, students began to crowd him—he needed to blame Hibari for making him hate crowded spaces. It was rather overwhelming, students asking him questions a mile a minute, until he felt a hand pull him away. A green haired girl was taking him out onto the campus. She was accompanied by her blue-eyes friend, the same one he noted asking if he was an assassin.

"You seemed overwhelmed, I'm Kayano," said the girl, yellow eyes filled with cheer. Despite the sincerity, he felt something off when she introduced herself. Her friend didn't seem to notice, and he figured that was the name she told others, "And that's Nagisa."

The said teen nodded in acknowledgement. Tsunayoshi could see the sharpness in Nagisa's eyes. This was a natural assassin, he realized. He glanced at Kayano, her bright eyes not as sharp, but there was _something_ about her that he knew was dangerous, something hidden.

"It's nice to meet you two, I'm Tsunayoshi," he said politely.

"You were trained by that guy? He's scary!" the girl continued. He nodded sheepishly. _More like, he's insane_. 

"Is he strong?" Nagisa finally spoke, growing curious by the minute.

"He wants to take upon the challenge," Kayano said, grinning.

He didn't take note of Nagisa's reaction to Kayano's exclaim, when he stood shocked. _Nagisa's a guy_?! Keeping composure, he let out a shaky chuckle in response. He felt fooled at the thought, after all, at first glance he looked like a girl. _Looks are deceiving. Should've known that since meeting Reborn._

"Yeah, Reborn's strong," Tsunayoshi confirmed.

"Do you want to fight, honestly?" Nagisa then asked.

"No, I don't like fighting," the Vongola Tenth admitted, sighing, "I only fight to protect my friends."

Both middle schoolers didn't respond, but seemed content with his response. He noticed them relax slightly. Perhaps they were stiff around him.

"But since Reborn put up the offer to you all, I can't say no. It's just a friendly spar," he added.

"You seem like a nice guy. I can't see you as a hitman," Kayano murmured. _I'm not a hitman, though_ , Tsunayoshi thought wryly.

"Do you guys want to kill your teacher?" Tsunayoshi asked curiously.

"Yeah," Nagisa responded absentmindedly, but then his face contorted to slight confusion. Did he really want to kill Koro-sensei? The young boss sensed the doubt, a small smile on his face.

"If you had the chance to save him, would you?"

Within a heartbeat, the answer from both of them was a _yes_. Tsunayoshi's smile grew wider, feeling comfortable.

 **Aaaand I'm leaving it here. I kind of want it open to interpretation how things go from there. If you want Tsuna to win or the 3-E students who challenge him to win ;)**


End file.
